Acid rain in Asia is likely to increase.

Economic expansion and continued reliance on coal as a primary fuel is likely to increase acid rain in Asia in the next two decades. By 2000, SO2 emissions in Asia will be greater than those of North America and Europe combined, according to recent World Bank projections, and emissions will continue growing rapidly, unless there are substantial investments in pollution control equipment. By 2020, Asian SO2 emissions could reach 110 million metric tons if no action is taken beyond current levels of control [8].

As a result, damage to natural ecosystems and crops is likely to increase dramatically. Large regions of southern and eastern China, northern and central Thailand, and much of the Korean peninsula could experience damaging sulfur deposition levels [9]. In some industrialized areas of China, for example, acid deposition levels may some day exceed those experienced in Central Europe’s “Black Triangle,” a large swath of Poland, the Czech Republic, and southeast Germany where both acid rain levels and forest damage were acute in the 1980s [10].

Damage could be largely avoided if modern pollution control technologies, such as flue-gas scrubbers, are widely adopted and if low-sulfur fuel is substituted where possible. In fact, the World Bank calculates that use of the best available pollution control technologies could cut acid deposition levels in half from 1990 levels by 2020 in Asia, even though energy use is projected to triple during this period. But the price for this level of environmental protection is steep: roughly US$90 billion per year throughout the Asia region, or about 0.6 percent of the region’s gross domestic product [11].

Less ambitious and lower-cost strategies can also cut acid-forming emissions substantially, but the amount of environmental protection these strategies buy is commensurately less and will not protect many areas from serious acid deposition. In the end, perhaps the most cost-effective option for controlling acid rain will be to adopt energy-efficiency measures that cut overall energy use and thus reduce emissions. If systematically employed, such energy-saving measures could cut control costs from one quarter to one third, according to the World Bank’s analysis; in addition, these measures would yield ancillary benefits such as better air quality and lower greenhouse gas emissions [12].

More to do in the developed world

In industrialized countries, environmental regulations restricting sulfur emissions and market forces that favor greater use of natural gas – which contains little sulfur – have proved relatively effective in cutting SO2 emissions. However, even this success may not be enough in some sensitive areas. A recent Canadian report concluded that SO2 emissions might have to fall another three quarters if ecosystems in a large area of southeastern Canada were to be adequately protected [13]. In addition,declines in SO2 emissions are likely to be partially offset in the future by emissions of NOx, which have remained broadly constant in the OECD countries since 1980. (See NOX Levels Are Still a Problem in Europe and North America

.) In much of Europe, NOx emissions are now creeping up again, due mainly to increased vehicle numbers and usage [14].

NOx Levels are still a problem in Europe and North America

Trends in SO2 and NOx Emissions in North America and Europe (OECD Countries Only), 1980-94

Source: Organisation for Economic Co-Operation and Development (OECD), OECD Environmental Data COmpendium 1997 (OECD, Paris, 1997); The Swedish Secretariat on Acid Rai, Acid News 5 (Int F